java - 未检测到 Java KeyPress

Question

当代码运行时，我没有收到任何错误。它运行除了我的按键之外的所有部分。哪里出了问题。

import javax.swing.*;
import java.awt.event.*;
import java.util.Scanner;

// Inheriting the JFrame class
public class Main extends JFrame {
    Scanner d = new Scanner(System.in);
    //Defining the Frame
    JFrame f;
    char input;
    int x = 250;
    int y = 100;

    //Constructor
    Main()
    {

        ImageIcon p = new ImageIcon("Player.png");
        JLabel b = new JLabel(p);
        b.setBounds(x, y, 50, 50);
        add(b);
System.out.println("started");


        b.addKeyListener(new KeyListener() {
            public void keyPressed(KeyEvent e) {

        System.out.println("*Event Listener Run*");
                input = e.getKeyChar();
                if (input == 'w')
                {
          y-=50;
                }
                else if (input == 'a')
                {
          x-=50;
                }
                else if (input == 's')
                {
          y+=50;
                }
                else if (input == 'd')
                {
          x+=50;
                }
            System.out.println("Cords: "+x+","+y);

        b.setBounds(x, y, 50, 50);
            }
            public void keyTyped(KeyEvent e){
      }
            public void keyReleased(KeyEvent e){
        System.out.println("keyReleased");
      }
        });

        //Set up Window
    System.out.println("*setup window*");
        setSize(800, 600);
        setLayout(null);
        setVisible(true);

    System.out.println("*setup window done*");
    }

  public static void main(String[] args){
    // Create the window
    new Main();
  }
}

我添加了 errorprintln以查看是否有一些代码没有运行，但一切都在运行。

标签： javaswinguser-interfacekeyevent

Answer 1

正如@this_is_cat 前面解释的那样，监听器需要在 JFrame 上而不是在 JLabel 上。

此外，使用 setLayout(null) 也不是好的做法，但在这里使用是因为我们只有一个组件可以使用。

package keylistener1;

import java.awt.Dimension;
import java.awt.HeadlessException;
import javax.swing.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.InputStream;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;

// Inheriting the JFrame class
public class KeyListener1 extends JFrame {

    private static final String ICON_FILE_PATH = "btn_home.gif";
//    Scanner d = new Scanner(System.in);
    private JLabel label = new JLabel("image not found");
    private JFrame jframe = new JFrame();

    private int xpos = 250;
    private int ypos = 250;

    public KeyListener1() throws HeadlessException {
        initFrame();
    }

    private JFrame initFrame() {

        jframe.setLayout(null);
        jframe.setPreferredSize(new Dimension(525, 525));
        jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jframe.setVisible(true);
        jframe.setTitle("Key Listener");

        // set up image icon
        Class cls = this.getClass();
        try (InputStream imageSource = cls.getResourceAsStream(ICON_FILE_PATH)) {
            BufferedImage bi = ImageIO.read(imageSource);
            ImageIcon p = new ImageIcon(bi);
            setLabel(new JLabel(p));
            getLabel().setBounds(getXpos(), getYpos(), 50, 50);
        } catch (IOException ex) {
            Logger.getLogger(KeyListener1.class.getName()).log(Level.SEVERE, null, ex);
        }

        initKeyListener();
        jframe.add(getLabel());
        jframe.pack();

        System.out.println("Starting coordinates: " + getXpos() + "," + getYpos());

        return jframe;
    }

    private void initKeyListener() {

        getJframe().addKeyListener(new KeyAdapter() {
            @Override
            public void keyTyped(KeyEvent e) {
                System.out.println("jf: " + e.getKeyChar());
                char input = e.getKeyChar();
                if (input == 'w') {
//                    ypos -= 50;
                    setYpos(getYpos() - 50);
                } else if (input == 'a') {
//                    xpos -= 50;
                    setXpos(getXpos() - 50);
                } else if (input == 's') {
//                    ypos += 50;
                    setYpos(getYpos() + 50);
                } else if (input == 'd') {
//                    xpos += 50;
                    setXpos(getXpos() + 50);
                }
                System.out.println("New Coordinates: " + getXpos() + "," + getYpos());

                getLabel().setBounds(getXpos(), getYpos(), 50, 50);
            }
        });
    }

    public JLabel getLabel() {
        return label;
    }

    public void setLabel(JLabel label) {
        this.label = label;
    }

    public int getXpos() {
        return xpos;
    }

    public void setXpos(int xpos) {
        this.xpos = xpos;
    }

    public int getYpos() {
        return ypos;
    }

    public void setYpos(int ypos) {
        this.ypos = ypos;
    }

    public JFrame getJframe() {
        return jframe;
    }

    public void setJframe(JFrame jframe) {
        this.jframe = jframe;
    }

    public static void main(String[] args) {
        new KeyListener1();
    }
}